Objective:

This study aims at improving our understanding and quantification of the potential effects of climate change on extreme meteorological events and air quality. Climate-induced changes in the following extreme events and their consequences for ozone and particulate matter (PM) air quality will be investigated: (a) heat waves, (b) temperature inversion, (c) atmospheric stagnation, and (d) lightning activities and associated wildfires.

Progress Summary:

Major accomplishments in year 3 (this report period) include:

We have investigated the impacts of extreme meteorological events on ozone and PM air quality based on the observational data in the U.S. region. Our statistical analysis shows that the average concentrations of air pollutants on days with extreme meteorological events are significantly (at 95% confidence interval) higher than those on non-event days. On the other hand, we have identified large seasonal and spatial variations in these effects. For example, the highest sensitivity of surface ozone to heat waves is found during summer and fall, in particular over the eastern U.S. where the average afternoon ozone levels are enhanced by more than 40% on days with heat waves. In contrast, the strongest impacts on PM from temperature inversion are observed in winter time with daily average PM2.5 concentrations enhanced by 40% or more for large areas in the United States. To better understand the mechanism/processes regulating the correlation between air pollutants and extreme air pollution meteorology, we have analyzed the sensitivities of individual PM2.5 species to various extreme air meteorological events.

We also examined the impacts on high pollution episodes from extreme air pollution meteorological events. Our results show significant enhancement in the probability of high pollution episodes (defined as the top 10% most polluted days) caused by the extreme air pollution meteorological events. Our results show that the occurrences of extreme air pollution episodes are very sensitive to the extreme meteorological events. For example, we find that in the United States, the probability of severe ozone pollution would be enhanced by up to 7 times when there are heat waves occurring in summer.

In addition, we have studied the synergistic effects of multiple types of extreme meteorological events occurring simultaneously. Our results could help us to quantify the changes in risk of severe air pollution in response to changes in meteorology and climate.

Based on simulation results from the CESM model, we have analyzed the potential trends of various extreme air pollution meteorological events in the future decades under the RCP4.5 scenario.

We have studied the sensitivities of wildfire occurrences to various factors in the context of global change.

Future Activities:

Continue analysis on the sensitivity of air quality (in particular the high pollution episodes) to extreme air pollution meteorology by incorporating data from a longer time period and combining model results with observational data.

Simulate the evolution of climate and air quality in the future decades and examine the long-term trends in extreme air pollution meteorology as well as the consequences for air quality. Particular attention will be given to the changes in severe air pollution episodes (e.g., the top 10% most polluted days for each season).

Develop a statistical model to evaluate the probability of severe air pollution episodes driven by extreme air pollution meteorological events. This model could be a very useful and convenient tool to examine the risk associated with extreme air pollution meteorology in the context of global change.

Continue our efforts in widely distributing project findings and sharing data generated from this project through i) peer-reviewed publications; ii) national and international conferences and workshops; and iii) collaboration with other research groups on related topics and research questions.

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.